The present invention relates to an apparatus and processes thereof for preparing toner particles for use, for example, in electrophotographic printing. More specifically, the invention relates to an apparatus and preparative processes for preparing toner particles with smooth surfaces.
A common shortcoming or problem associated with related prior art toner particle production methods using, for example, comminutive methodologies, that is, where a mixture of a resin and a pigment are melt mixed into a mass and thereafter chopped up and subsequently pulverized by grinding and thereafter classified to a relatively narrow range of particles sizes, is that the resulting toner particles are disadvantaged by, for example, the toner particles having a relatively rough or uneven surface characteristic. This uneven or rough surface characteristic can cause the toners to have a number of undesirable or disadvantageous properties. These negative properties include, for example, poor and uneven flow characteristics; uneven or irregular compression and packing characteristics; and irregular charging and discharging properties. These negative properties can degrade the quality of the developablity and imaging performance of the toner particles in various imaging processes and apparatuses. The problem of rough or irregular toner particle surfaces and concomitant negative attributes is not unique to particles obtained by comminutive methodologies and may also be associated with other toner formation process, such as the so-called xe2x80x9cchemical tonersxe2x80x9d including emulsion-aggregation type toner particle formation processes where the toner is comprised of many smaller particles assembled into larger aggregates.
In U.S. Pat. No. 4,209,550, issued Jun. 24, 1980, to Hagenbach et al., there is disclosed coated carrier materials prepared by electrostatically attracting particles of a coating material to the surface of carrier cores and then heating the carrier materials causing the coating material to fuse to the carrier material forming an adherent coating thereon. The coating material is attracted to the carrier materials by (a) rolling carrier materials down an inclined plane while spraying the carrier materials with a coating material; (b) dropping carrier materials through a cloud chamber containing a cloud of coating material particles; and (c) solids blending a mixture of carrier materials and particles of coating material.
In U.S. Pat. No. 4,935,326, issued Jun. 19, 1990, to Creatura et al., there is disclosed a carrier and developer composition, and a process for the preparation of carrier particles with substantially stable conductivity parameters comprising: 1) providing carrier cores and a polymer mixture; 2) dry mixing the cores and the polymer mixture; 3) heating the carrier core particles and polymer mixture, whereby the polymer mixture melts and fuses to the carrier core particles; and 4) thereafter cooling the resulting coated carrier particles.
In U.S. Pat. No. 4,333,743, issued Jun. 8, 1982, to Nojima, there is disclosed a method of producing sand-blasting abrasive materials, and the materials so produced, consisting of silica sand and/or slag, coated with a thermosetting resin by heat treatment, and the coating being then rendered unsoluble and unmeltable, by subsequent, separate heat treatment. The resin may contain a catalyst.
In U.S. Pat. No. 5,412,185, issued May 2, 1995, to Sturman et al., there is disclosed an induction heating method and apparatus for coating polymers onto electrically conductive fibers. This is accomplished with an apparatus having a mandrel for supporting a composite workpiece and a helical induction coil disposed around the mandrel. The mandrel, workpiece and induction coil are disposed in an autoclave. The mandrel is a hollow, porous member having a port formed therein which is connected to a vacuum. A vacuum bag is hermetically sealed on the mandrel so as to define an enclosure over the workpiece. A power source is connected to the induction coil and, when activated, causes the coil to generate an oscillating magnetic field lying along the longitudinal axis of the mandrel. The magnetic field induces heat-generating eddy currents in the fibers of the workpiece which are oriented orthogonally to the magnetic field.
In U.S. Pat. No. 3,650,798, issued Mar. 21, 1972, to Case et al., there is disclosed a method for the coating of running strands or webs with a thermoplastic protective layer. The successive steps comprise the application of a primer and the hot air current drying and curing of same supplemented by inductive heating. The temperature is next raised in two successive stages by inductive type heaters, the later stage while the strand or web is vertically traversing the length of a continuously replenished dense cylindrical bed of powdered vinyl polymer or the like. The replenishment as well as cooling of the powder is accomplished through a recirculatory arrangement powered by air nozzles. Alternate coating materials are proposed including polyolefins containing compounds of metal.
In U.S. Pat. No. 4,233,387, issued Nov. 11, 1980, to Mammino et al., there is disclosed electrostatographic coated carrier particles for use in the development of electrostatic latent images prepared by mixing carrier core materials with powdered thermoplastic resin particles having a size of between 0.1 micron and about 30 microns. The carrier core materials are mixed with the resin particles until the resin particles mechanically and/or electrostatically adhere to the core materials and the mixture is heated to a temperature of between 320xc2x0 F. and 650xc2x0 F., for between 120 minutes and 20 minutes so that the resin particles melt and fuse to the carrier core materials. The coated carrier particles are cooled, classified to the desired particle size, and mixed with finely-divided toner particles to form a developer mixture. The process is especially advantageous for coating carrier particles with resin materials having poor solubility characteristics.
The aforementioned patents are incorporated by reference herein in their entirety.
There remains a need for improved toner manufacturing processes, and particularly comminutive toner manufacturing processes that produce relatively smooth surface toner particles with superior particle properties, and development and imaging characteristics, especially for fine toner particles with a narrow size distribution and for color toners used in high fidelity digital imaging processes and equipment.
The apparatus, processes thereof, and the smooth surface toner particle products resulting therefrom, of the present invention are useful in many applications including imaging and printing processes, including color printing, for example, electrostatographic, such as in xerographic printers and copiers, including digital systems.
Embodiments of the Present Invention, Include:
An apparatus comprising:
a grinder adapted to grind toner particles;
a classifier in communication with the grinder adapted to separate sized toner particles from unsized toner particles;
a conduit in communication with the classifier which conduit is adapted to convey the sized toner particles away from the grinder;
a heater adapted to heat and smooth the surface of the sized toner particles received from the conduit; and
a particle separator adapted separate the resulting mixture of smooth surface toner particles and debris particles received from the heater;
A process, accomplished in the aforementioned apparatus, comprising:
grinding toner particles comprising a resin component and a magnetic pigment;
separating classified toner particles from the resulting ground particles;
transporting the separated classified toner particles and heating the separated classified toner particles with a non-contact induction heater surrounding at least a portion of the conduit to partially melt the resin component and causing the surface of the toner particles to smooth; and
optionally isolating the resulting smooth surface toner particles; and
An apparatus comprising:
a housing;
a high intensity mixing tool within the housing adapted to mechanically fluidize and blend toner particles;
a conduit in communication with the housing, adapted to convey toner particles away from the housing and to a receiver; and
an induction heater surrounding at least a portion of the housing adapted to heat and smooth the surface of the toner particles while the particles are fluidized and blended.
These and other embodiments are illustrated herein.